Implement drag files from kupfer's window #158
Description
On similar quazi-modal launcher's like quicksilver, a user can drag a file brought up from the launcher window and drop it somewhere else. As someone that's used quicksilver for a decade, this usecase is extremely useful for instances where one wants to say, drop a screenshot into an attachment, drop a file into a gnome-files window that's already open, etc.
Environment
Ubuntu 21.04 (wayland)
Actual Behaviour
Dragging a file or folder from kupfer doesn't appear to have any effect.
Expected Behaviour
Dragging a file or folder from kupfer should be possible and show appropriate visual cues similar to dragging and dropping a file when using a file manager.